流感:pandemics of the past

Here we learn how flu has affected us in the past. Georgia Mills investigates...

Georgia - It may be a current problem but flu is not a new disease. Greek physician Hippocrates described the symptoms roughly 2,400 years ago, and epidemics, which are severe outbreaks in communities, are documented throughout history.

But sometimes a new strain can go global, and cause what’s known as a pandemic. The first evidence of a pandemic was in 1580, but the most deadly and infamous one to date was 100 years ago this year. The Spanish Flu. This has been described as the greatest medical holocaust in history, killing more people than World War One. It’s estimated between 2.5% and 5% of the world’s population died, and what made this pandemic especially unusual is that the victims were mostly young adults; more normally, flu is a major risk for the very young and the very old.

Pandemics are usually caused when a strain of flu affecting birds or pigs jumps into humans. These can then spread like wildfire because no one in the population is immune to them. This was behind the Spanish Flu pandemic, and more recently the 2009 “swine flu”, which came from – you guessed it - *pig snort*

While flu pandemics occur around every 30 years, none have been as severe as the Spanish flu, perhaps in part due to the development of the first flu vaccine, in 1938. Vaccines work by feeding your immune system small or inactive bits of the virus, so it can learn what the agent looks like, and be ready to destroy it, should the infection be encountered for real.

So if we have a vaccine, why does the flu keep coming back? This is because, unfortunately, flu is always one step ahead. The virus grows rapidly, and as it does so it regularly makes genetic spelling mistakes called “mutations”. These alter the appearance of the virus as it spreads through the population, giving it a molecular “facelift” that means the immune system struggles to recognise it again later.

This is why you need a new flu jab every year, because the vaccine is constantly being checked and updated to make sure that it provides protection against the circulating strains of flu that you are most likely to encounter. But, because vaccines need to be made well ahead of flu season, scientists have to predict what the flu strains will look like when they arrive. Most of the time they get it right, but sometimes the virus behaves unexpectedly, meaning the vaccines aren’t fully effective.